Holder for the carbon brushes of rotary electrical machines



P 9- J. A. c. MALCHUS 8 ,9

HOLDER FOR THE CARBON BRUSHES v ROTARY ELECTRICAL MACHINES Filed Jan. 25, l947 FIG 1' 11w: M: of

lt wb Patented Sept. 27, 1949 HOLDER FOR THE CARBON BRUSHES F ROTARY ELECTRICAL MACHINES Johannes Andries Christiaan Malchus, Amsterdam, Netherlands Application January 25, 1947, Serial No. 724,358 In the Netherlands April 6, 1945 Section 1. Public Law 690, August 8, 1946 Patent expires April .6, 1965 4 Claims.

' This invention relates to holders for the carbon brushes of rotary electrical machines, which expression includes electric motors and generators and combinations thereof of all types using such carbon brushes. It has particular application to such machines which are comparatively small in size and deliver or consume a relatively small electric current.

It has been previously proposed to provide carbon brush holders of the kind comprising an integral tubular body of electrically insulating material to accommodate the brush, a terminal member electrically connected with the brush, a connecting element for connection to, or forming part of, an electric circuit, and a press member co-acting with the body and adapted to press the terminal member into contact with the connecting element. Y

Known constructions of this kind are, however, attended by the disadvantage that they are comparatively complex. In one such construction, for example, the connecting element consists of a metal disc provided with an aperture, through which the brush can pass, and formed with two metal strips extending at right angles from the disc in the direction of the commutator, the ends of these strips adjacent the commutator being turned outwardly so as to project from the side of the tubular body at the commutator end thereof, thus providing soldering tags. The strips are disposed in grooves in the interior of the tubular body. The terminal memher, to which the brush spring is anchored is arranged between this disc and the press member, which is in the form of a screw cap so that when it isscrewed down it presses the terminal member into contact with the disc to connect the latter electrically with the brush. This arrangement makes it necessary for the connecting element to have the special shape described and also gives the tubular body of the holder is, more complex construction, owing to the grooves having to be provided therein. The result is that manufacture is made comparatively dii'flc'ult. Further difliculties are liable to arise in use, because when the cap forming the press member is screwed down it is liable to cause the terminal member to turn by friction, whereby the usual metal braid connecting the brush with the terminal member is twisted and shortened, thus reducing the eifective length of the brush. Also, assembly of the holder and attachment of a conductor to the connecting element isnot very simple.

The present invention has for its object to provide a brush holder of simplified construction designed to avoid the disadvantages of known constructions.

According to the present invention, in a brush holder of the kind above referred to, the side wall of the tubular body has at least one slot at the endadjacent the press member, through which slot or slots the connection of the connecting element to an external circuit is adapted to be made.

The arrangement may be such that the connecting elementis adapted to be introduced and gripped between the terminal member and the press member, and the tubular body may have an internal shoulder upon which the terminal member abuts, the slot or slots extending from a point level with the abutment face of the shoulder to the open end of the body adjacent the press member. This facilitates connection of the brush to the circuit, because the connecting element can be soldered or otherwise secured to a conductor of the circuit and then inserted into the body of the holder, or alternatively the conductor itself can serve as the connecting element and be inserted into the body of the holder. This is not possible with the known construction above referred to, as the conductor must be secured to the specially shaped connecting element with the latter already in position in the body, and if this is done by soldering there is a risk of solder getting on the brush holder and adjacent parts, e. g. the commutator. According to a further feature of the invention, the circuit connecting element may comprise a disc secured against rotation in the body by engagement in the slot or slots. Thus, for example the disc of the connecting element may be provided with one or more lugs projecting into the slot or slots and adapted'to serve as soldering tags.

One'embodiment of the invention will now be described by way of example with reference to the accompanying drawings, wherein:

Fig. 1 is a sectional elevation of a brush holder mounted'on a rotary electrical machine, the section being taken axially of the machine.

Fig. 2 is a sectional elevation of the body-a the holder alone, the section being taken in a plane perpendicular to that of Fig. l and Fig. 3 shows a plan View of a connecting element.

The machine in this embodiment is a small electric motor or generator as used in domestic or industrial appliances or for similar purposes. Only parts of the armature I and the commutator 2 of the machine are shown in Fig. 1. In an aperture in the casing 3 of the machine there is mounted the body 4 of the brush holder, which is moulded of electrically insulating material and is secured in the casing 3 by a grub screw 5. The body is of tubular form to accommodate the carbon brush 6 which is pressed into contact with the commutator 2 by a spring l4. A flexible bonding braid l electrically connects the brush 6 with a terminal member 8 on which the spring I4 is anchored. This terminal member abuts on a shoulder formed by an internal enlargement in the tubular body 4. The top of the terminal member 8 is in contact with a connecting element 9 connected to a conductor Ill of an external electric circuit. The enlarged end of the i body 4 is internally screw-threaded to receive a press member II in the form of a screw-cap. The terminal member 8 and the connecting element 9 are pressed into firm electrical contact with one another by screwing the cap ll into the top of the body holder 4. As can be seen from Figs. 1 and 2, the top of the body is provided with an elongated slot [2 in its side wall which extends axially of the body from its open top down to the level of the shoulder on which the terminal member 8 rests.

The connecting element 9 is in the form of a disc having a lug l3 (see Fig. 3) which projects into the lateral slot l2 (see Fig. 2). The disc may be soldered to the conductor I0. In this way it is possible to effect the soldering operation outside the holder and then to insert the disc 9 into the body of the holder. Alternatively, the bared end of the conductor itself can be introduced into the body 4 and clamped between the press member H and the disc 9, or two such discs 9 1 may be provided between which the end of the conductor I0 is clamped, or again the disc 9 may be dispensed with altogether, the end of the conductor itself forming the connecting element and being inserted and clamped between the terminal member 8 and the cap ll direct. Whichever method is adopted, assembling is a very simple operation.

The projecting lug l3 secures the disc 9 against rotation in the body by engagement in the slot l2. The lug [3 need not project right through, but can stop about half-way in, the slot so that the insulation of the conductor Hi can continue into the slot, as shown in Fig. 1, which provides a convenient safeguard against accidental contact with live parts, so avoiding any risk of shock and earthing.

As shown in the drawings, and particularly in Fig. 2, the tubular body 4 of the brush holder can have its internal diameter narrowed at the bottom, i. e. adjacent the commutator, to provide two spring abutments for the spring 15. This limits the outward movement of the spring and prevents it from coming into contact with the commutator if the brush should be completely worn away. These abutments can be easily formed in the moulding operation and do not en- .tail any complications in the manufacture thereof.

It may be desirable to provide more than one 4 slot, such as for connection of shunt circuits, and in that event the disc of the connecting element, if used at all, would be provided with a corresponding number of appropriately disposed lugs without detriment to the simplicity oi. its manufacture, which may be by stamping out of sheet metal.

It will be seen that in the above construction the body of the holder is of a particularly simple shape, much more so .than in the known construction above referred to, because no internal grooves are necessary whereas one or more lateral slots are quite easy to form in the casting or moulding process. Similarly, all the other parts of the holder, notably the connecting element and the terminal member, are simple and easy to manufacture sothat the holder is quite cheap to produce. manufacture of the component parts, the assembling operation is also much simpler compared with known constructions, as will have been appreciated from the above description. Moreover, interposition of the connecting element between the press member and the terminal member practically eliminates the risk of the latter turning with the press member and so twisting and shortening the bonding braid connecting the terminal member with the brush.

What I claim is: M

1. A holder for a carbon brush of a rotary electrical machine comprising an integral body of electrically insulating material having a bore with a threaded portion of increased sectional area and a press member adapted to be screwed therein, to cooperate with a shoulder provided in the bodybetween the threaded portion and the remainder of the bore, said body being adapted to accommodate not only a brush assembly consisting of a brush, one end of which being connected by a spring to a disc-shaped terminal member for supplying current to said brush and adapted to be clamped between said shoulder and said press member, but also a connecting element adapted to be introduced between the press member and the terminal member and adapted to be connected to at least one electric circuit, the threaded portion of the insulating body having at least one slot throughwhich the connection of the connecting element to an electrical circuit is adapted to be made.

2. A holder for a carbon brush as claimed in claim 1, wherein the connecting element comprises a disc which is locked against rotation in the body by engagement in at least one of the slots.

3. A holder for acarbon brush as claimed in claim 2, wherein the connecting element is provided with at least one lug projecting into one of the slots.

4. A holder for a carbon brush of a rotary electrical machine comprising an integral body of electrically insulating material having a bore with a threaded portion of increased sectional area and a press member adapted to be screwed therein, to cooperate with a shoulder provided in the body between the threaded portion and the remainder of the bore, said body being adapted to accommodate not only a brush assembly consisting of a brush, one end of which being connected by a spring to a disc-shaped terminal member for supplying current to -said brush and adapted to be clamped'between said-shoulder and said press member, but also a connecting element "adapted to be introducedbetween the press member and the terminal member and adapted to be con:

Apart from these advantages in the- JOHANNES ANDRIES CHRISTIAAN MALCHUS.

REFERENCES CITED The following references are of record in the file of this patent:

5 UNITED STATES PATENTS Number Name Date 1,457,896 Cook June 5, 1923 2,135,303 Greene Nov. 1, 1938 10 FOREIGN PATENTS Number Country Date 210,529 Great Britain Feb. 1, 1924 

